U.S. patent application number 15/749583 was filed with the patent office on 2019-01-17 for pipeline descaling and rock stratum fracturing device based on electro-hydraulic pulse shock waves.
The applicant listed for this patent is HUAZHONG UNIVERSITY OF SCIENCE AND TECHNOLOGY. Invention is credited to Hua LI, Zhiyuan LI, Fuchang LIN, Siwei LIU, Yi LIU, Yuan PAN, Qin ZHANG.
Application Number | 20190017362 15/749583 |
Document ID | / |
Family ID | 61750649 |
Filed Date | 2019-01-17 |
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United States Patent
Application |
20190017362 |
Kind Code |
A1 |
LIU; Yi ; et al. |
January 17, 2019 |
PIPELINE DESCALING AND ROCK STRATUM FRACTURING DEVICE BASED ON
ELECTRO-HYDRAULIC PULSE SHOCK WAVES
Abstract
The invention discloses a pipeline descaling and rock stratum
fracturing device based on electro-hydraulic pulse shock waves,
comprising a ground low-voltage control device, a transmission
cable and an electro-hydraulic pulse shock wave transmitter. The
invention generates available high-strength shock waves with
repetition frequency to bombard a specific position of the pipeline
or rock stratum so as to achieve the effect of pipeline descaling
and rock stratum fracturing; the breakdown field strength of the
liquid gap can be effectively reduced to improve the conversion
efficiency of the electrical energy to the mechanical energy of the
electro-hydraulic pulse shock wave so as to obtain a high-strength
electro-hydraulic pulse shock wave; the transmitting cavity adopts
a parabolic focusing cavity, and through refraction and reflection
of the rotating parabolic cavity, the shock wave is focused in a
preset direction and radiates outwards to act on the pipeline dirt
or rock stratum while ensuring that the shock wave has no
longitudinal component and does not will not damage the liquid
within the pipeline and the pipeline sheath, so that the effect of
pipeline descaling or rock stratum fracturing is improved after
focusing. The invention has the advantages of effectively removing
the pipeline dirt, fracturing the rock stratum and improving the
permeability as well as high reliability, environmental
friendliness and low cost.
Inventors: |
LIU; Yi; (Wuhan, Hubei,
CN) ; LIN; Fuchang; (Wuhan, Hubei, CN) ; PAN;
Yuan; (Wuhan, Hubei, CN) ; ZHANG; Qin; (Wuhan,
Hubei, CN) ; LI; Hua; (Wuhan, Hubei, CN) ; LI;
Zhiyuan; (Wuhan, Hubei, CN) ; LIU; Siwei;
(Wuhan, Hubei, CN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
HUAZHONG UNIVERSITY OF SCIENCE AND TECHNOLOGY |
Wuhan, Hubei |
|
CN |
|
|
Family ID: |
61750649 |
Appl. No.: |
15/749583 |
Filed: |
September 29, 2016 |
PCT Filed: |
September 29, 2016 |
PCT NO: |
PCT/CN2016/100725 |
371 Date: |
February 1, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B08B 9/0326 20130101;
B08B 7/026 20130101; E21B 28/00 20130101; E21B 37/00 20130101; E21B
43/26 20130101; B08B 9/02 20130101; E21B 43/003 20130101 |
International
Class: |
E21B 43/26 20060101
E21B043/26; E21B 28/00 20060101 E21B028/00; E21B 43/00 20060101
E21B043/00 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 27, 2016 |
CN |
201610853849.2 |
Claims
1. A pipeline descaling and rock stratum fracturing device based on
electro-hydraulic pulse shock waves, comprising: a ground
low-voltage control device, an electro-hydraulic pulse shock wave
transmitter placed in the pipeline or rock hole, and a logging
cable for connecting the ground low-voltage control device to the
electro-hydraulic pulse shock wave transmitter; the
electro-hydraulic pulse shock wave transmitter includes: a high
voltage converting unit, a high-temperature energy storage unit, a
pulse compression unit, an electro-hydraulic pulse shock wave
transmitting unit and a protection unit which are coaxially
distributed in sequence along the axis; the high voltage converting
unit is configured to convert an AC low voltage signal transmitted
by the logging cable into a direct current high voltage signal; the
high-temperature energy storage unit is configured to temporarily
store the direct current high voltage energy output by the high
voltage converting unit as the total electric energy for the
electro-hydraulic pulse discharge for a long time; the pulse
compression unit is configured to control the energy stored in the
high-temperature energy storage unit to be instantaneously applied
to the electro-hydraulic pulse shock wave transmitting unit; the
electro-hydraulic pulse shock wave transmitting unit is configured
to generate a strong shock wave in a discharge liquid with weak
compressibility by a large pulse current due to breakdown of the
electro-hydraulic pulse shock wave discharge gap under the action
of a high voltage, and allow the generated shock wave to propagate
outwards; the shock wave radiates in a preset focused direction
through the focusing cavity, and is transferred into the oil and
gas pipeline or the rock hole to touch the pipeline dirt or allow
rock crack creation or fracturing; the protection unit is
configured to ensure coaxality of the motion in the pipeline so as
to avoid collision of the instrument with the pipeline wall.
2. The pipeline descaling and rock stratum fracturing device of
claim 1, wherein when the pipeline descaling and rock stratum
fracturing device acts on a horizontal oil and gas pipeline or rock
hole, the electro-hydraulic pulse shock wave transmitter further
includes: a crawler configured to allow the electro-hydraulic pulse
shock wave transmitter to crawl to a target position to be
processed in the oil and gas pipeline or rock hole.
3. The pipeline descaling and rock stratum fracturing device of
claim 1, wherein the pulse compression unit includes a pulse
compression switch and a control loop thereof; the pulse
compression switch may be a gas switch, a vacuum trigger switch or
other high-voltage solid switches; the control loop is used for
outputting a trigger signal to allow the pulse compression switch
to be rapidly turned on.
4. The pipeline descaling and rock stratum fracturing device of
claim 1, wherein the electro-hydraulic pulse shock wave
transmitting unit includes: a discharge liquid, a high-voltage
electrode and a low-voltage electrode; the high-voltage electrode
and the low-voltage electrode are both immersed in the discharge
liquid, and the high-voltage electrode and the low-voltage
electrode are coaxially distributed along the same geometric
central axis; the gap is broken down by the high field strength
between the high-voltage electrode and the low-voltage electrode to
form the arc, and the arc rapidly expands to form a pulse shock
wave which then propagates outwards.
5. The pipeline descaling and rock stratum fracturing device of
claim 4, wherein the electro-hydraulic pulse shock wave
transmitting unit further includes: an insulating fixing member
sleeved on the high-voltage electrode and/or the low-voltage
electrode and coaxially distributed with the high-voltage electrode
or the low-voltage electrode.
6. The pipeline descaling and rock stratum fracturing device of
claim 5, wherein the high-voltage electrode is a needle electrode
wrapped by the insulating fixing member and exposing an end
portion, and the low-voltage electrode is a plate electrode.
7. The pipeline descaling and rock stratum fracturing device of
claim 5, wherein the high-voltage electrode is a needle electrode
wrapped by the insulating fixing member and exposing an end
portion, and the low-voltage electrode is a needle electrode.
8. The pipeline descaling and rock stratum fracturing device of
claim 5, wherein the insulating fixing member and the plate
low-voltage electrode are respectively processed to form an upper
focusing cavity and a lower focusing cavity according to the same
parabolic curve equation.
9. The pipeline descaling and rock stratum fracturing device of
claim 8, wherein the parabolic curve equation is y.sup.2=a(x+b),
where y is the central axis of the high-voltage electrode, x is the
horizontal symmetry axis of the upper focusing cavity and the lower
focusing cavity, and a and b are constants.
10. The pipeline descaling and rock stratum fracturing device of
claim 5, wherein the material of the insulating fixing member is a
high-strength insulating material with high temperature resistance
and corrosion resistance such as a material of heat shrink tubing,
epoxy, polyoxymethylene or polyether ketone.
Description
BACKGROUND OF THE INVENTION
Field of the Invention
[0001] The invention relates to the fields of high voltage
technology, pulse power technology, oil and gas exploitation and
rock fracture, and more particularly, to a pipeline descaling and
rock stratum fracturing device based on electro-hydraulic pulse
shock waves.
Description of the Related Art
[0002] Rapid arc discharge induced by the high voltage takes place
in the liquid, and rapid expansion of the arc channel and liquid
vaporization and expansion will result in outward radiation of a
strong shock wave, which is one of the physical effects of the
"electro-hydraulic effect." The mechanical effect of the
"electro-hydraulic effect" is widely used in the areas of pipeline
descaling, rock fracturing and crack creation, oil well plug
removal and so on.
[0003] At present, conventional means of increasing production by
oil and gas pipeline descaling mainly include chemical plug
removal, fracturing plug removal, ultrasonic plug removal and the
like. The methods of chemical plug removal and fracturing plug
removal are gradually eliminated due to the complicated operation
process and serious environmental pollution; the method of
ultrasonic plug removal is difficult to generate strong ultrasonic
waves in a high hydrostatic pressure environment of the oil and gas
pipeline, and thus the plug removal effect is limited. In addition,
the rock stratum fracturing technology generally has the problems
of slow speed, long period, high cost and so on, and the rock
fracturing cost in oil and gas stimulation is more than half of the
exploration cost. The traditional rock breaking method by TNT
explosives is poor in controllability of blasting and seriously
pollutes the environment; the rock breaking method by ultrasonic
mechanical energy and the like has the problems of low efficiency
of rock breaking and so on.
[0004] At present, one of the bottlenecks that limit further
application of the electro-hydraulic pulse shock waves is how to
obtain high-strength pulse shock waves and how to control
orientation and focused radiation of them accurately. Conventional
methods for generating electro-hydraulic pulse shock waves are that
the pulse power supply is applied to the underwater inter-electrode
gap formed by the discharge electrodes. The electrodes are usually
in the form of rod-plate electrodes, plate-plate electrodes and so
on, and the high voltage electrode and the low voltage electrodes
are directly exposed in the discharge liquid. Thus, the strongest
point of the electric field is the tip of the anode and the
cathode, and the length of the arc is approximately the minimum
inter-electrode gap distance. Meanwhile, since the discharge
electrodes for the generation of the pulse shock waves are placed
directly in the liquid, the size of ends of the electrodes exposed
in the liquid is large, leading to too large leakage energy in the
liquid breakdown process and large breakdown distribute dispersion.
When the plate-plate electrodes are used, the arc position is not
fixed, and it is difficult to accurately regulate the shock wave;
the plate-plate gap has a certain restraint on the shock wave
propagation, while the breakdown electric field strength between
the inter-electrode is relatively high, and the gap distance is
relatively small, so that the length of the pulse arc is relatively
short, the energy injection into the liquid gap is relatively low,
and thus the energy conversion efficiency cannot be improved to
generate a stronger shock wave. The use of needle-needle electrodes
can reduce the breakdown field strength of the liquid gap to a
certain extent, but the ablation performance of the needle
electrodes is poor, which leads to the significant decrease of the
life of the shock wave generator. In some cases of high hydrostatic
pressure, the breakdown becomes more difficult, and simply use of
the needle-needle electrodes may cause electric field distortion,
thus limiting the effect of reducing the breakdown field.
SUMMARY OF THE INVENTION
[0005] In view of the defects of serious environmental pollution,
low efficiency and poor controllability in the existing oil and gas
pipeline descaling for increase in production and rock stratum
fracturing technology, the present invention provides a pipeline
descaling and rock stratum fracturing device based on
electro-hydraulic pulse shock waves, which has the advantages of
simple structure, good versatility and significant shock wave
focusing and orienting radiation effect as well as being
environmentally friendly, high-efficiency and easy to
operation.
[0006] According to the invention, there is provided a pipeline
descaling and rock stratum fracturing device based on
electro-hydraulic pulse shock waves, comprising: a ground
low-voltage control device, an electro-hydraulic pulse shock wave
transmitter placed in the pipeline or rock hole and a logging cable
for connecting the ground low-voltage control device to the
electro-hydraulic pulse shock wave transmitter; the pulse shock
wave transmitter includes: a high voltage converting unit, a
high-temperature energy storage unit, a pulse compression unit, a
liquid-electric pulse shock wave transmitting unit and a protection
unit which are coaxially distributed in sequence along the axis;
the high voltage converting unit is configured to convert an
alternating current (AC) low voltage signal transmitted by the
logging cable into a direct current (DC) high voltage signal; the
high-temperature energy storage unit is configured to temporarily
store the DC high voltage energy output by the high voltage
converting unit as the total electric energy for the pulse
discharge; the pulse compression unit is configured to control the
energy stored in the high-temperature energy storage unit to be
instantaneously applied to the pulse shock wave transmitting unit;
the pulse shock wave transmitting unit is configured to generate a
strong shock wave in a liquid with weak compressibility by a large
pulse current under the action of a high voltage, and allow the
generated shock wave to propagate outwards; the shock wave radiates
in a preset focused direction through the focusing cavity, and is
transferred into the oil and gas pipeline or the rock hole to touch
the pipeline dirt or allow rock crack creation or fracturing; the
protection unit is configured to ensure coaxality of the motion in
the pipeline so as to avoid collision of the instrument with the
pipeline wall. In addition, the ground low-voltage control device
is configured to set the discharge voltage and the discharge times
so as to achieve a good mechanical action effect; the logging cable
is configured to transmit a power frequency low voltage to the
pulse shock wave transmitter; the pulse shock wave transmitter is
configured to generate a high-strength shock wave and allow the
shock wave to orientatedly radiate outwards through a rotating
parabolic cavity, and the shock wave acts on the pipeline to remove
dirt or bombard the rock to form cracks. Based on efficient
structure design of the electro-hydraulic pulse shock wave
transmitter, the arc regulation technology and the shock wave
focusing and oriented radiation control technology, the effect of
pipeline descaling and rock stratum fracturing can be achieved.
[0007] Further, when the pipeline descaling and rock stratum
fracturing device acts on a horizontal oil and gas pipeline or rock
hole, the electro-hydraulic pulse shock wave transmitter further
includes: a crawler configured to allow the electro-hydraulic pulse
shock wave transmitter to crawl to a target position to be
processed in the oil and gas pipeline or rock hole.
[0008] Further, the electro-hydraulic pulse shock wave transmitter
can act on a vertical oil and gas pipeline or rock hole. In this
case, the electro-hydraulic pulse shock wave transmitter goes deep
into the pipeline or the rock hole to a fixed position under the
action of its own gravity to complete the pulse discharge, and each
discharge produces at least one shock wave, which effectively
propagates in the radial direction to bombard the pipeline dirt or
break the rock. In addition, the electro-hydraulic pulse shock wave
transmitter can also act on a horizontal oil and gas pipeline or
rock hole. In this case, the electro-hydraulic pulse shock wave
transmitter crawls to a target position and each pulse discharge
produces at least one shock wave, which effectively propagates in
the radial direction to bombard the pipeline dirt or break the
rock.
[0009] Further, the pulse compression unit includes a pulse
compression switch and a control loop thereof; the pulse
compression switch may be a gas switch, a vacuum trigger switch or
other high-voltage solid switches; the control loop is used for
outputting a trigger signal to allow the pulse compression switch
to be rapidly turned on.
[0010] Further, the electro-hydraulic pulse shock wave transmitting
unit includes: the discharge liquid, a high-voltage electrode and a
low-voltage electrode; the high-voltage electrode and the
low-voltage electrode are both immersed in the discharge liquid,
and the high-voltage electrode and the low-voltage electrode are
coaxially distributed along the same geometric central axis; the
arc is formed by the high electric field strength between the
high-voltage electrode and the low-voltage electrode and rapidly
expands to form a pulse shock wave.
[0011] Further, the electro-hydraulic pulse shock wave transmitting
unit further includes: an insulating fixing member sleeved on the
high-voltage electrode or the low-voltage electrode and coaxially
distributed. The electrodes are wrapped by the insulating fixing
member with only the end portions of the electrodes exposed, or
only one electrode is wrapped by the insulating fixing member with
the end portion of the wrapped electrode exposed; the form of
wrapping the electrode by the insulating fixing member in the
discharge electrodes is suitable for any type of electrodes such as
needle-needle electrodes, rod-rod electrodes, needle-plate
electrodes. In addition, when only one electrode is wrapped by the
insulating fixing member, the effect is independent of the polarity
of the electrode, that is, the effect of improving the shock wave
strength can be achieved whether the high-voltage electrode or the
low-voltage electrode is wrapped.
[0012] Specifically, the high-voltage electrode is a needle
electrode wrapped by the insulating fixing member with the exposed
tip of the electrode and the low-voltage electrode is a plate
electrode.
[0013] Further, the insulating fixing member and the plate
electrode are respectively processed to form an upper focusing
cavity and a lower focusing cavity according to the same parabolic
curve equation.
[0014] In addition, the high-voltage electrode and the low-voltage
electrode are coaxially distributed along the same geometric
central axis, and the insulating fixing member or the plate
low-voltage electrode is provided to form a rotating focusing
cavity surface, so that by controlling geometrical parameters of
the rotating focusing cavity, it is convenient to allow
near-spherical shock waves generated between the high-voltage
electrode and the low-voltage electrode to radiate in a preset
focusing direction through the focusing cavity.
[0015] Preferably, the parabolic curve equation is y.sup.2=a(x+b),
where y is the central axis of the high-voltage electrode, x is the
horizontal symmetry axis of the upper focusing cavity and the lower
focusing cavity, and a and b are constants.
[0016] Further, the material of the insulating fixing member is
heat shrink tubing, epoxy, polyoxymethylene or polyether ketone.
The insulating fixing member for wrapping the electrode may be any
material with a certain mechanical strength and electrical
insulation strength, such as heat shrink tubing, epoxy,
polyoxymethylene or polyether ketone.
[0017] According to the parameters of the rotating parabolic cavity
and the geometrical size of the electro-hydraulic pulse shock wave
transmitting unit, the maximum action area of the shock wave
transmitting unit can be determined, and according to the action
range and action distance of the shock wave, the parameters can be
optimized, so that the shock wave strength can be effectively
increased and the mechanical effect of the shock wave can be
improved.
[0018] Compared with the prior art, the invention has the following
advantage effects:
[0019] (1) according to the pipeline descaling and rock stratum
fracturing device based on electro-hydraulic pulse shock waves
provided in the invention, since the arc regulation technology and
the shock wave focusing and orienting radiation control technology
are adopted, it not only can effectively remove the pipe dirt,
fracturing the rock stratum and improve the permeability, but also
has characteristics of simple operation, high reliability,
environmental friendliness, low cost and so on.
[0020] (2) according to the discharge electrode adopting arc
regulation technology provided in the invention, the
inter-electrode electric field distribution is distorted, and thus
the length of the development path of the discharge arc is
obviously higher than the minimum inter-electrode gap distance, so
that the length and impedance of the electro-hydraulic pulse arc is
increased, the injected energy of the gap is improved, and thus
effects of improving the shock wave energy conversion efficiency
and improving the shock wave strength are achieved.
[0021] (3) according to the transmitting cavity adopting the shock
wave focusing and orienting radiation control technology provided
in the invention, a focusing cavity surface of the insulating
fixing member is employed, which can lengthen the smallest distance
along the surface between the high-voltage electrode and the
low-voltage electrode to increase the breakdown voltage
therebetween, so that the electrical insulation strength of the
transmitting cavity is enhanced. Also, the geometric center of the
initial arc is located exactly at the focal point of the focusing
cavity formed by the plate electrode and the insulating fixing
member, which greatly improving the shock wave strength.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] FIG. 1 is a schematic structural diagram of a pipeline
descaling and rock stratum fracturing device based on
electro-hydraulic pulse shock waves according to the invention, in
which (a) shows a case where the pulse shock wave transmitter acts
on a vertical oil and gas pipeline or rock hole; and (b) shows a
case where the pulse shock wave transmitter acts on a horizontal
oil and gas pipeline or rock hole.
[0023] FIG. 2 is a schematic structural diagram of an
electro-hydraulic pulse shock wave transmitter in the pipeline
descaling and rock stratum fracturing device based on
electro-hydraulic pulse shock waves according to the invention.
[0024] FIG. 3 is a schematic diagram showing a case where the
discharge electrodes adopt the arc regulation technology in the
pipeline descaling and rock stratum fracturing device based on
electro-hydraulic pulse shock waves according to the invention, in
which (a) is a schematic diagram of the arc development without the
arc regulation technology, and (b) is a schematic diagram of the
arc development with the arc regulation technology.
[0025] FIG. 4 is a schematic diagram of modified discharge
electrodes in the pipeline descaling and rock stratum fracturing
device based on electro-hydraulic pulse shock waves according to
the invention, in which (a) is a schematic structural diagram
showing a case where a high-voltage electrode and a low-voltage
electrode are both wrapped by the insulating fixing member; (b) is
a schematic structural diagram showing a case where the
high-voltage electrode is wrapped by the insulating fixing member
and the low-voltage electrode is a rod electrode; and (c) is a
schematic structural diagram showing a case where the high-voltage
electrode is wrapped by the insulating fixing member and the
low-voltage electrode is a plate electrode.
[0026] FIG. 5 is a schematic diagram illustrating typical waveforms
of voltages, currents and shock waves without and with electrode
modification in the pipeline descaling and rock stratum fracturing
device based on electro-hydraulic pulse shock waves according to
the invention, in which (a) is a schematic diagram of the typical
waveforms of the discharge voltage, the current and the shock wave
without the arc regulation technology; (b) is a schematic diagram
of a typical waveforms of the discharge voltage, the current and
the shock wave with the arc regulation technology.
[0027] FIG. 6 is a schematic diagram illustrating the arc
development images without and with electrode modification in the
pipeline descaling and rock stratum fracturing device based on
electro-hydraulic pulse shock waves according to the invention, in
which (a) is a schematic diagram of the arc development images
without the arc regulation technology; and (b) is a schematic
diagram of the arc development images with the arc regulation
technology.
[0028] FIG. 7 is a scatter diagram of test results of the shock
wave strength without and with the arc regulation technology in the
pipeline descaling and rock stratum fracturing device based on
electro-hydraulic pulse shock waves according to the invention.
[0029] FIG. 8 is a schematic diagram illustrating a distribution
rule of breakdown delays without and with electrode modification in
the pipeline descaling and rock stratum fracturing device based on
electro-hydraulic pulse shock waves according to the invention.
[0030] FIG. 9 is a schematic diagram illustrating a corresponding
relationship between the shock wave strength and the arc length and
peak current value in the pipeline descaling and rock stratum
fracturing device based on electro-hydraulic pulse shock waves
according to the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0031] For clear understanding of the objectives, features and
advantages of the invention, detailed description of the invention
will be given below in conjunction with accompanying drawings and
specific embodiments. It should be noted that the embodiments
described herein are only meant to explain the invention, and not
to limit the scope of the invention.
[0032] The invention provides a pipeline descaling and rock stratum
fracturing device based on electro-hydraulic pulse shock waves,
comprising: a ground low-voltage control device 100, a transmission
cable 200 and an electro-hydraulic pulse shock wave transmitter
300. The ground low-voltage control device 100, the transmission
cable 200 and the electro-hydraulic pulse shock wave transmitter
300 are ensured to have good electrical insulation and mechanical
strength through oil well joints. According to actual working
conditions of the pipeline or rock, by controlling the ground
low-voltage control device 100, the electro-hydraulic pulse shock
wave transmitter 300 can be allowed to generate shock waves 400 so
as to control the strength, the number of times and the repetition
frequency of the shock waves, so that the optimal effect of
pipeline descaling or rock stratum fracturing 500 is achieved.
[0033] The core of the invention lies in the structure design, the
arc regulation technology and the radiation direction control of
the shock wave induced by the pulse shock wave transmitter 300 so
as to achieve objectives of bombardment or breaking of the pipeline
or the rock at a specific position. The specific working process of
the invention is: according actual working conditions, the job
specification of plug removal for production increase is made; the
optimal type of the discharge electrodes of the electro-hydraulic
pulse shock wave transmitter 300 is determined and each
electro-hydraulic pulse discharge generates one effective
high-strength shock wave, which then expands outwards in a
near-spherical manner; through refraction and reflection of the
rotating parabolic cavity, the radial shock wave is focused in a
horizontal direction and radiates outwards to act on the oil and
gas pipeline or the rock hole such that the blockage attached
around the pipe is broken and then enters the oil well under the
hydrostatic pressure, so that pipeline descaling is achieved; the
shock wave acts on the surface of the rock stratum such that
gradually deepened and penetrating plane cracks, which extend in a
radial direction, occur in the rock, and multiple strong shock
waves enable the rock to be fractured.
[0034] The electro-hydraulic pulse shock wave transmitter 300 is
used for generating a high-strength shock wave and allowing the
shock wave to radiate in a preset direction through the rotating
parabolic cavity so as to act on the pipeline to remove dirt for
oil and gas production increase or bombard the rock to achieve rock
crack creation or fracturing.
[0035] The electro-hydraulic pulse shock wave transmitter 300 can
act on a vertical oil and gas pipeline or rock hole. In this case,
the electro-hydraulic pulse shock wave transmitter 300 goes deep
into the pipeline or the rock hole to a fixed position under the
action of its own gravity to complete the pulse discharge, and at
least one effective horizontal focused shock wave is generated to
bombard the pipeline or break the rock.
[0036] The electro-hydraulic pulse shock wave transmitter 300 can
act on a horizontal oil and gas pipeline or rock hole. In this
case, the electro-hydraulic pulse shock wave transmitter 300 may go
to a target position of the pipeline or the rock hole by virtue of
a crawler, and at least one effective vertical focused shock wave
is generated to bombard the pipeline or break the rock.
[0037] The electro-hydraulic pulse shock wave transmitter 300
according to the invention comprises: a high voltage converting
unit 301, a high-temperature energy storage unit 302, a pulse
compression unit 303, an electro-hydraulic pulse shock wave
transmitting unit 304 and a protection unit 305. The respective
units of the electro-hydraulic pulse shock wave transmitter are
coaxially distributed along the axis, which is beneficial to
increase of the overall mechanical strength. In the
electro-hydraulic pulse shock wave transmitter, the protection unit
305 is configured to ensure coaxality of the motion in the pipeline
so as to avoid collision of the instrument with the pipeline wall;
the high voltage converting unit 301 is configured to efficiently
convert an AC low voltage transmitted by the logging cable into a
DC high voltage through a full bridge or half bridge rectification
manner; the high-temperature energy storage unit 302 adopts a
multi-cascaded pulse capacitor unit which has short-circuit current
impact resistance, excellent high temperature performance and long
service life, and is configured to temporarily store the DC voltage
energy output by the high voltage converting unit 301 as the total
electric energy for the electro-hydraulic pulse discharge for a
long time; and the pulse compression unit 303 is configured to
control the energy stored in the high-temperature energy storage
unit to be instantaneously applied to the electro-hydraulic pulse
shock wave transmitting unit.
[0038] The pulse compression unit 303 includes a pulse compression
switch and a control loop thereof, and the ground low-voltage
control device 100 applies a trigger control signal transmitted by
the special transmission cable to a preset trigger terminal of the
pulse compression switch, in which the pulse compression switch may
be a gas switch, a vacuum trigger switch or other high-voltage
solid switches, and the control loop is used for outputting a
trigger signal to allow the pulse compression switch to be rapidly
turned on.
[0039] The working process of the electro-hydraulic pulse shock
wave transmitting unit 304 is: the electro-hydraulic pulse shock
wave discharge gap is broken down under the action of a high
voltage, and through the resulting large pulse current, a strong
shock wave is generated in the discharge liquid with weak
compressibility and propagates outwards; the shock wave radiates in
a preset focused direction through the focusing cavity, and is
finally transferred to the oil and gas pipeline or the rock hole to
touch the pipeline dirt or enable the rock crack creation or
fracturing.
[0040] The electro-hydraulic pulse shock wave transmitting unit 304
includes a discharge liquid 3040, a high-voltage electrode 3041, a
low-voltage electrode 3042 and the insulating fixing member 3044;
the high-voltage electrode 3041 and the low-voltage electrode 3042
are coaxially distributed along the axis, and the insulating fixing
member 3044 and the high-voltage and low-voltage electrodes 3041,
3042 are coaxially distributed; and the high-voltage and
low-voltage electrodes 3041, 3042 are both immersed in the
discharge liquid to constitute the electro-hydraulic pulse shock
wave transmitting unit 304.
[0041] The pipeline descaling and rock stratum fracturing device
based on electro-hydraulic pulse shock waves according to the
invention adopts the arc regulation technology, in which the
high-voltage electrode 3041 and the low-voltage electrode 3042 are
both wrapped by the insulating fixing member 3044 with only the
ends of the electrodes exposed, or one of the high-voltage
electrode 3041 and the low-voltage electrode 3042 is wrapped by the
insulating fixing member 3044 with only the end of the wrapped
electrode exposed; in this case, the inter-electrode electric field
distribution of the space charge attached to the insulation surface
is distorted, the arc would develop along the distortion point of
the electric field and thus due to the action of the coulomb force,
the length of the arc is significantly larger than the minimum
inter-electrode gap distance, which is beneficial to increase of
the shock wave strength.
[0042] In addition, the form of wrapping the electrode by the
insulating fixing member 3044 in the arc regulation technology is
suitable for any type of electrodes such as needle-needle
electrodes, rod-rod electrodes, needle-plate electrodes and
plate-plate electrodes.
[0043] In addition, when only one electrode is wrapped by the
insulating fixing member 3044 in a case of adopting the arc
regulation technology, the effect is independent of the polarity of
the electrode. To a certain extent, the effect of improving the
shock wave strength can be achieved whether the high-voltage
electrode 3041 or the low-voltage electrode 3042 is wrapped.
[0044] In addition, in a case of adopting the arc regulation
technology, the insulating fixing member 3044 for wrapping the
electrode may be any material with a certain mechanical strength
and electrical insulation strength, such as heat shrink tubing,
epoxy, polyoxymethylene or polyether ketone.
[0045] In the pipeline descaling and rock stratum fracturing device
based on electro-hydraulic pulse shock waves according to the
invention, the transmitting cavity adopts the shock wave focusing
and orienting radiation control technology, in which the rod
high-voltage electrode 3041 and the plate low-voltage electrode
3042 are coaxially distributed along the same geometric central
axis, the high-voltage electrode 3041 is wrapped by the insulating
fixing member 3044 and the low-voltage electrode 3042 is directly
exposed in the discharge liquid 3040. The insulating fixing member
3044 and the plate low-voltage electrode 3042 are respectively
processed to form an upper focusing cavity and a lower focusing
cavity according to the same parabolic curve equation, and
according to the linear reflection law, the spherical shock wave at
the focus point parallelly radiates in the cavity opening direction
though the reflecting action of the focusing cavity, so that
focusing and orienting radiation control of the shock wave is
achieved.
[0046] In addition, the cavity surface of the parabolic focusing
cavity formed by the insulating fixing member 3044 and the
low-voltage electrode 3042 is formed by rotating the parabolic
curve equation is y.sup.2=a(x+b), where y is the central axis of
the high-voltage electrode, x is the horizontal symmetry axis of
the upper focusing cavity and the lower focusing cavity, and a and
b are constants.
[0047] In addition, the geometric center of the focusing cavity is
located exactly on the axis of the shock wave transmitter 300 whose
diameter is a certain value, and thus by setting the opening
coefficients a and b of the parabola, the maximum opening diameter
d of the rotating parabolic focusing cavity and the maximum action
area s can be determined. In a case where the energy of the
electro-hydraulic pulse shock wave and the action distance are both
constant, the maximum action area s of the shock wave transmitting
unit determines the energy density at the shock wave action point.
Therefore, according to actual working conditions of the shock wave
transmitter 300 and the required energy density, the action range
and the action distance of the shock wave can be determined, and
thus the proper opening diameter d of the focusing cavity can be
set so as to achieve the optimal shock wave focusing and orienting
effect.
[0048] In addition, since the breakdown distance along the surface
is increased due to the focusing cavity surface of the insulating
fixing member 3044, the electric insulation strength can be
improved; the geometric center of the initial arc is located
exactly at the focal point of the focusing cavity formed by the
plate electrode and the insulating fixing member to improve the
shock wave strength, thereby achieving the optimal focusing
effect.
[0049] FIG. 1 shows structures of the pipeline descaling and rock
stratum fracturing devices based on electro-hydraulic pulse shock
waves, in which (a) of FIG. 1 shows a case where the pulse shock
wave transmitter acts on a vertical oil and gas pipeline or rock
hole; and (b) of FIG. 1 shows a case where the pulse shock wave
transmitter acts on a horizontal oil and gas pipeline or rock hole.
For ease of description, detailed description are provided below
with reference to the accompanying figures and specific
examples.
[0050] The structures of two pipeline descaling and rock stratum
fracturing devices based on electro-hydraulic pulse shock waves in
(a) and (b) of FIG. 1 both have a ground low-voltage power supply
control device 100, a logging cable 200 and a electro-hydraulic
pulse shock wave transmitter 300. The ground low-voltage power
supply control device can adopt an AC generator of 220V/50 Hz as
the power supply, and the generator has a power of not less than 10
kW and is east to transport and operate. The ground low-voltage
power supply control device converts a power frequency voltage of
220V into an adjustable intermediate frequency voltage of 0-1.8 kV
with a frequency of 1 kHz. The logging cable has a rated voltage of
6 kV and a resistance of 30 .OMEGA./km. The other end of the
logging cable is connected to the electro-hydraulic pulse shock
wave transmitter through a universal interface of the oil well.
[0051] The two differ in that the shock wave transmitter in (a) of
FIG. 1 acts on a vertical oil and gas pipeline or rock hole and can
be located in a working position by virtue of its own gravity,
while the shock wave transmitter in (b) of FIG. 1 acts on a
horizontal oil and gas pipeline or rock hole and in this case,
crawls to a target position by virtue of a crawler 306 which is
connected between the logging cable 200 and the electro-hydraulic
pulse shock wave transmitter 300. If the electro-hydraulic pulse
shock wave transmitter 300 needs to be placed in the horizontal oil
and gas pipeline or rock hole, an instruction is issued to open
four draft arms of the crawler 306 such that four road wheels of
the crawler 306 are tightly pressed against the inner wall of the
oil well casing or the rock hole. The four road wheels of the
crawler 306 are driven by a mechanical drive device to walk along
the casing so that the logger is conveyed to a designated location.
When the logger reaches the predetermined position, the crawler
stops walking and retracts the draft arms. At this time, the
electro-hydraulic pulse shock wave transmitter 300 starts the
electro-hydraulic pulse discharge operation. Each pulse discharge
produces at least one shock wave which effectively radiates in a
preset direction to bombard the pipeline or fracture the rock
stratum, so as to achieve the pipeline descaling or the rock crack
creation or fracturing.
[0052] The pipeline descaling and rock stratum fracturing device
according to the invention is the core of the invention, and its
structure is shown in FIG. 2. Specifically, the electro-hydraulic
pulse shock wave transmitter 300 includes: a high voltage
converting unit 301, a high-temperature energy storage unit 302,
pulse compression unit 303, an electro-hydraulic pulse shock wave
transmitting unit 304 and a protection unit 305, in which the
protection unit 305 is configured to ensure coaxality of the motion
in the pipeline so as to avoid collision of the instrument with the
pipeline wall; the high voltage converting unit 301 is configured
to convert a low voltage with power frequency into a high voltage
with medium-high frequency and then output a DC high voltage after
rectification; the high-temperature energy storage unit 302 is
configured to temporarily store the DC voltage energy output by the
high voltage converting unit 301 as the total electric energy for
the electro-hydraulic pulse discharge for a long time; the pulse
compression unit 303 is configured to control the energy stored in
the high-temperature energy storage unit 302 to be instantaneously
applied to the electro-hydraulic pulse shock wave transmitting unit
304; and a high-strength shock wave, which is radiated by the arc
passage induced by the inter-electrode high electric field of the
electro-hydraulic pulse shock wave transmitting unit 304,
propagates in a focus-controllable direction. In addition, the
basic parameters of the electro-hydraulic pulse shock wave
transmitter 300 are: an outer diameter of 102 mm and a total length
of 5.7 m. The DC voltage output by the high voltage converting unit
is 30 kV. The high-temperature energy storage unit has a
single-stage capacitance of 1.5 .mu.F and a rated voltage of 30 kV.
In the present embodiment, the high-temperature energy storage unit
adopts two-stage cascade connection, and has a capacitance of 3.0
.mu.F, a rated stored energy of 1.35 kJ, a rated working
temperature of 120.degree. C., and a service life of more than
10,000 times. The pulse compression unit adopts a vacuum trigger
switch with a rated voltage of 30 kV, a maximum current peak value
of 50 kA and a charge transferring amount of greater than 100
kC.
[0053] Schematic diagrams of arc development of the
electro-hydraulic pulse shock wave transmitting unit 304 without
and with the arc regulation technology are respectively shown in
(a) and (b) of FIG. 3. The electro-hydraulic pulse shock wave
transmitting unit 304 includes the discharge liquid 3040, a
high-voltage electrode 3041, a low-voltage electrode 3042 and so
on, whether the arc regulation technology is employed or not. In a
case of adopting the arc regulation technology, the high-voltage
electrode 3041 and the low-voltage electrode 3042 are wrapped by
the insulating fixing member 3044 on the outside. The length of the
arc 3043 shown in (a) of FIG. 3 is approximately equal to the
shortest inter-electrode distance, while the length of the
development path of the discharge arc 3043 in (b) of FIG. 3 in a
case of adopting the arc regulation technology is significantly
larger than the minimum inter-electrode gap distance due to the
fact that the inter-electrode electric field distribution of the
space charge attached to the insulation surface is distorted and
the arc would develop along the distortion point of the electric
field. Therefore, in a case of adopting the arc regulation
technology, the length of the arc can be increased to increase the
length and impedance of the electro-hydraulic pulse arc and improve
the injected energy of the gap so as to achieve effects of
improving the shock wave energy conversion efficiency and improving
the shock wave strength.
[0054] In the electro-hydraulic pulse shock wave transmitting unit
304, as shown in (a) of FIG. 4, the high-voltage electrode 3041 and
the low-voltage electrode 3042 can be wrapped by the insulating
fixing member, or as shown in (b) and (c) of FIG. 4, only the
high-voltage electrode is wrapped and the tip of the low-voltage
electrode may be set to be a rod or plate electrode. The
high-voltage electrode 3041 and the low-voltage electrode 3042 are
coaxially distributed along the axis, and the insulating fixing
member 3044 and the high-voltage and low-voltage electrodes 3041,
3042 are coaxially distributed. The high-voltage electrode 3041 and
the low-voltage electrode 3042 are both immersed in the discharge
liquid 3040. In addition, the plate low-voltage electrode 3042 and
the insulating fixing member 3044 may be designed as a rotated
parabolic focusing cavity, as shown in (c) of FIG. 4. The
insulating fixing member 3044 and the plate low-voltage electrode
3042 are respectively processed to form an upper focusing cavity
and a lower focusing cavity according to the same parabolic curve
equation. According to the linear reflection law, the spherical
shock wave at the focus point parallelly radiates in the cavity
opening direction though the reflecting action of the focusing
cavity, so that focusing and orienting radiation control of the
shock wave is achieved. According to actual working conditions of
the shock wave transmitter 300 and the required energy density, the
action range and the action distance of the shock wave can be
determined, and thus the proper opening diameter d of the focusing
cavity can be set so as to achieve the optimal shock wave focusing
and orienting effect.
[0055] In this embodiment, the typical discharge voltages, currents
and shock wave waveforms without and with the arc regulation
technology are shown in (a) and (b) of FIG. 5, respectively. It can
be seen that when the conventional discharge electrode is employed,
the breakdown delay is obviously higher than that in a case of
adopting the arc regulation technology, the energy consumed by the
pre-breakdown process is larger, the energy conversion efficiency
is lower and thus the shock wave strength is lower. In a case of
adopting the arc regulation technology, the horizontal distance
between the shock wave measurement probe and the middle of the
shock wave transmitter is 17 cm, the measured strength of the shock
wave is about 6 MPa and the pulse width is about 50 .mu.s. When the
discharge electrode with the arc regulation technology is employed,
the maximum liquid gap that can be broken down is about twice that
in a case of employing the conventional electrode, which
corresponds to that the breakdown field strength is reduced to half
of the original.
[0056] (a) and (b) of FIG. 6 show schematic diagrams of the arc
development trend without and with the arc regulation technology in
this embodiment, respectively. It can be seen that after adopting
the arc regulation technology, the inter-pole arc length is
increased from 17 mm to 28 mm, and the arc is changed into a curved
type from a linear type. At this time, the injected energy of the
arc channel transformed from the total electric energy in gap
breakdown is increased from about 3% to 10%, and the shock wave
strength is improved by about 1 time.
[0057] FIG. 7 is a scatter diagram of test results of the shock
wave strength without and with the arc technology in the invention.
The average value of the shock wave strength without the arc
regulation technology is about 3.55 MPa, while the average value of
the shock wave strength with the arc regulation technology is about
6.74 MPa. It can be seen from the test results that the average
value of the shock wave strength is increased from 3.55 MPa to 6.74
MPa after the arc regulation technology is employed, that is, the
shock wave strength enhancement effect is remarkable.
[0058] FIG. 8 is a schematic diagram showing a distribution rule of
pre-breakdown delays in a case of different types of electrodes in
this embodiment. The results show that when the conventional
discharge electrode is employed, not only the average pre-breakdown
delay reaches hundreds of microseconds, but also the dispersion is
very large; in a case of adopting the arc regulation technology,
whether the needle-needle electrodes are employed or the
needle-plate electrodes are employed and whether the high-voltage
and low-voltage discharge electrodes are wrapped with only ends of
the electrodes exposed, or only the high-voltage discharge
electrode is wrapped with only the end of the wrapped electrode
exposed, the average breakdown delay is only about ten
microseconds, and has good consistency.
[0059] FIG. 9 is a schematic diagram illustrating a corresponding
relationship between the shock wave strength and the arc length and
current peak value with the arc regulation technology in this
embodiment. As the arc length increases, the current peak value
gradually decreases, and the shock wave strength trends to
increase. The strength of the electro-hydraulic pulse shock wave
increases with the increase of the energy injected into the gap,
and the energy injected into the gap is closely related to the
impedance of the electro-hydraulic pulse arc, so that the larger
the impedance of the arc is, the larger the injected energy is.
[0060] In order to verify the effect of pipeline descaling and rock
stratum fracturing produced by this electro-hydraulic pulse shock
wave, preliminary test simulation is performed on this device in an
atmospheric environment with room temperature and normal pressure.
In the test, the electro-hydraulic pulse shock wave transmitter is
located in the center of the oil well pipeline or the rock hole.
The cement cylinder is used to simulate the oil well pipeline
structure, a stainless steel inner cylinder is provided inside the
cement cylinder and holes with a diameter of 20 mm are opened on
the surface to simulate perforation. The inner and outer cement
layer thickness is 12 mm, and after the action of one
electro-hydraulic pulse shock wave, the blockage holes in the
action range of the electro-hydraulic pulse shock wave are dredged
by 100%. A rock sample with an outer diameter of 670 mm, an inner
diameter of 130 mm and a height of 500 mm is used to simulate the
fracturing effect of the device on the rock. With the increase of
number of times of discharge, longitudinally penetrating cracks
from the inside to the outside occurs in the rock sample, and after
about 20 times of discharge, the rock sample is fractured along the
longitudinally penetrating cracks so that the effect of rock crack
creation and fracturing.
[0061] While particular embodiments of the invention have been
shown and described, it will be obvious to those skilled in the art
that changes and modifications may be made without departing from
the spirit and scope of the invention.
* * * * *